From d9061fef9a7109c32d7e4eb1d42e387b9781e92a Mon Sep 17 00:00:00 2001
From: Phil Elwell <phil@raspberrypi.com>
Date: Wed, 12 Jan 2022 08:23:28 +0000
Subject: [PATCH] spi: gpio: Add sck-idle-input property

The sck-idle-input property indicates that the spi-gpio driver should
return the SCK line to an input when the chip select signals are
inactive.

Signed-off-by: Phil Elwell <phil@raspberrypi.com>
---
 drivers/spi/spi-gpio.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

--- a/drivers/spi/spi-gpio.c
+++ b/drivers/spi/spi-gpio.c
@@ -35,6 +35,7 @@ struct spi_gpio {
 	struct gpio_desc		*sck;
 	struct gpio_desc		*miso;
 	struct gpio_desc		*mosi;
+	bool				sck_idle_input;
 	struct gpio_desc		**cs_gpios;
 };
 
@@ -225,8 +226,12 @@ static void spi_gpio_chipselect(struct s
 	struct spi_gpio *spi_gpio = spi_to_spi_gpio(spi);
 
 	/* set initial clock line level */
-	if (is_active)
-		gpiod_set_value_cansleep(spi_gpio->sck, spi->mode & SPI_CPOL);
+	if (is_active) {
+		if (spi_gpio->sck_idle_input)
+			gpiod_direction_output(spi_gpio->sck, spi->mode & SPI_CPOL);
+		else
+			gpiod_set_value_cansleep(spi_gpio->sck, spi->mode & SPI_CPOL);
+	}
 
 	/* Drive chip select line, if we have one */
 	if (spi_gpio->cs_gpios) {
@@ -235,6 +240,9 @@ static void spi_gpio_chipselect(struct s
 		/* SPI chip selects are normally active-low */
 		gpiod_set_value_cansleep(cs, (spi->mode & SPI_CS_HIGH) ? is_active : !is_active);
 	}
+
+	if (spi_gpio->sck_idle_input && !is_active)
+		gpiod_direction_input(spi_gpio->sck);
 }
 
 static int spi_gpio_setup(struct spi_device *spi)
@@ -323,6 +331,7 @@ static int spi_gpio_request(struct devic
 	if (IS_ERR(spi_gpio->miso))
 		return PTR_ERR(spi_gpio->miso);
 
+	spi_gpio->sck_idle_input = device_property_read_bool(dev, "sck-idle-input");
 	spi_gpio->sck = devm_gpiod_get(dev, "sck", GPIOD_OUT_LOW);
 	return PTR_ERR_OR_ZERO(spi_gpio->sck);
 }
